December to March is the best time to visit Thailand and Vietnam on one trip. In December and January, Bangkok is at its driest and coolest, Chiang Mai at its coolest, Ho Chi Minh City is in its dry season and Hanoi is cool. For beaches, pair Phuket, driest in January and February, with Phu Quoc or southern Vietnam, and leave Ko Samui and Da Nang for February onward.
If you can only pick one month, make it February. It's the driest month of the year on Ko Samui (57.8 mm), in Da Nang (22 mm) and in Ho Chi Minh City (8 mm), and Phuket averages 25.8 mm. The catch: in 2027, Tet takes over Vietnam from February 4 to 10.
Peak, Shoulder and Wet Seasons: Why December to March Wins
Peak season for a two-country trip is December to March, when the dry seasons overlap. Bangkok's 1961 to 1990 normals give 10 mm of rain in December and 9 mm in January, and Ho Chi Minh City's 1991 to 2020 normals show 12 mm in January and 8 mm in February. Ko Samui and Da Nang join from February, and in 2027, Tet falls inside the window.
The shoulders are April to May and November. April is the hottest month in both Bangkok, with average highs of 34.9°C (94.8°F), and Chiang Mai, at 36.1°C (97.0°F), and by May Phuket's rain has climbed to 269.8 mm. Vietnam's tourism authority rates March to May as its best weather countrywide. November is dry in Hanoi (48 mm) but the wettest month on Ko Samui.
The wet season runs May to October in most of Thailand, per UK travel advice. In Vietnam, Canada puts the monsoon at June to September in the north and south and October to December in the center, with typhoons from June to December.
Thailand by Region: Bangkok, the North and Two Coasts
Thailand's regions dry out at different times, and the Gulf coast runs months behind the rest.
Bangkok and the Central Plains: Dry From December
Bangkok's 1961 to 1990 normals fall from 242 mm in October to 48 mm in November and 10 mm in December, then stay at 30 mm or less a month through March, so the city works as a bookend for either country from November through March. September is the wettest month, at 344 mm, and December the coolest, with average lows of 20.8°C and highs of 31.3°C.
Chiang Mai and the North: Cool Mornings, Then Smoke
Chiang Mai is the place to be in December and January. Its long-term averages give January lows of 14.2°C (57.6°F) and December lows of 15.3°C, with 7.7 mm of rain in January, the driest month, so pack a warm layer for early starts in the hills. The rains peak in August, at 224.6 mm.
⚠️ The north's dry season comes with smoke. Canada's travel advice warns that seasonal smog during the dry season is recurrent and agricultural burning also hits air quality in the northern provinces, including Chiang Mai. Monitor air-pollution levels, as Canada advises, especially if you have a respiratory condition. With April also the hottest month there, at 36.1°C, go early in the dry season rather than at its end.
Phuket and the Andaman Coast: Best in January and February
Phuket's long-term averages give 23.3 mm of rain in January and 25.8 mm in February, with December (61.9 mm) and March (59.0 mm) still good beach months. The rains arrive hard in May and peak in September at 386.5 mm.
Ko Samui and the Gulf Coast: Wet When Phuket Is Dry
Ko Samui's heaviest rain lands from October to December, 290.2 mm, 489.6 mm and 209.1 mm, and January is still wet at 137.8 mm. February is the driest month at 57.8 mm, and March (77.8 mm) and April (76.6 mm) stay dry enough for a beach week.
Vietnam in Brief: Three Regions, Three Calendars
Vietnam's north, center and south peak at different times. For a Thailand pairing, this is the short version; our guide to the best time to visit Vietnam goes month by month.
The north is cool and mostly dry from November to January. Hanoi's 1991 to 2020 normals give January lows of 14.6°C (58.3°F) and highs of 20.0°C (68.0°F), with 48 mm of rain in November and 24 mm in December. February and March stay light on rain but average 12 and 18 rain days, counting any day with 0.1 mm or more, so expect drizzle and gray skies.
The center keeps a calendar much like Ko Samui's. Da Nang averages 658 mm of rain in October, 486 mm in November and 272 mm in December, then dries out to 22 mm in February, 36 mm in March and 50 mm in April.
The south is the easiest match for Thailand. Ho Chi Minh City is dry from December to April and wettest in September, and Vietnam's tourism authority says Phu Quoc is at its best in December and January, with its rainy season from July to September.
⚠️ Skip central Vietnam in October and November. Canada's travel advice notes seasonal flooding in central Vietnam in October and November and warns that roads may become impassable. Move the Hue, Hoi An and Da Nang leg to February or later.
Beach Pairings: Matching Thailand's Coasts to Vietnam's
The rule is simple once you see the two clocks: Thailand's Andaman coast pairs with Vietnam's south, and its Gulf coast pairs with Vietnam's center. For specific stretches of sand, see our guide to the best beaches in Vietnam.
December and January: Phuket with Phu Quoc or the south. Phuket's two driest months line up with Phu Quoc's best months and Ho Chi Minh City's dry season, while Ko Samui and Da Nang are still wet.
February to April: Ko Samui with Da Nang and Hoi An. Both hit their driest in February, at 57.8 mm and 22 mm, and stay dry through April. Phuket works until March, then its rain rises to 137.8 mm in April.
November: Phuket, not Ko Samui or Da Nang. Phuket averages 173.7 mm, just over a third of Ko Samui's 489.6 mm, while Da Nang gets 486 mm. Vietnam's tourism authority puts Phu Quoc's clear, sunny months at October to June, so it pairs too.
June to August: Ko Samui with central Vietnam. Ko Samui stays at 122.8 mm a month or less while Phuket gets 236.9 mm to 284.1 mm, and Da Nang gets 68 mm, 92 mm and 167 mm with June highs of 34.9°C. It's typhoon season, so keep plans flexible.
Planning by Priority: What to Do in Which Month
If one thing matters more than the rest, plan around it.
| If Your Priority Is… | Go In… | Avoid… |
|---|---|---|
| Phuket beaches with Phu Quoc or the south | December to February | May to October |
| Ko Samui beaches with Da Nang and Hoi An | February to April | October to December |
| Cities: Bangkok, Hanoi, Ho Chi Minh City | December to February | July to October |
| Cool air in the north: Chiang Mai, Hanoi | November to January | April (heat), July and August (rain) |
| A summer beach trip | June to August, Ko Samui with Da Nang | Phuket and Hanoi in the same months |
Route order follows the same logic. On a December or January trip, start in Chiang Mai while it's cool, work south through Bangkok to Phuket, then fly on to Ho Chi Minh City or Phu Quoc. On a February to April trip, build around Ko Samui and central Vietnam, and fit Hanoi at either end.
Festivals Worth Planning Around: Songkran, Loi Krathong and Tet
Three festivals are worth building dates around, or dodging. Songkran, the Thai New Year, runs April 13 to 15 nationwide. Loi Krathong falls on the full moon of the 12th month of the Thai lunar calendar, usually in November. Tet, Vietnam's Lunar New Year, falls on February 6, 2027, and the public-sector break runs February 4 to 10.
Tet matters for the paperwork too. Three working days is the statutory standard for an eVisa decision, and 3 to 5 working days is what usually happens; Tet and public holidays push it further. Processing times are set by Vietnam Immigration, so for an early-February 2027 trip, apply in January.
Getting Between Them: Fly, Because the Cambodia Route Is Shut
Thailand and Vietnam fit easily into one trip, as long as you fly. Our Vietnam itinerary ideas help you decide where to land.
⚠️ Don't book a bus that crosses from Thailand into Cambodia. The UK's advice, updated October 12, 2026, says land borders and crossings between Thailand and Cambodia remain suspended. A ticket that depends on that crossing won't get you to Ho Chi Minh City, whatever an older guide says.
One shortcut is Bangkok to Phu Quoc. A daily nonstop between the two began on August 8, 2026, with a flight time the Tourism Authority of Thailand puts at 1 hour 20 minutes. Phu Quoc lets you stay up to 30 days without a visa, on the island only, flying direct or connecting through another Vietnamese international airport's transit area.
That exemption is narrower than it sounds. Going on to the mainland without a visa breaks the rules and can bring a fine of VND 3 to 5 million. Switching to a domestic flight in Ho Chi Minh City or Hanoi means clearing immigration, which needs a visa or exemption. If Phu Quoc is your only Vietnam stop, fly direct; if it's the first of several, get the eVisa.
Visas and Arrival Forms: Vietnam's eVisa, Thailand's 30 Days
Citizens of every country and territory can apply for a Vietnam eVisa, the rule since August 15, 2023. It can be valid for up to 90 days, with single or multiple entry, and it's issued to people outside Vietnam, so apply before you travel. The government's own eVisa site is evisa.gov.vn.
Some passports don't need it. Germany, France, Italy, Spain, the UK, Russia, Japan, South Korea, Denmark, Sweden, Norway and Finland get up to 45 days visa-free, for any purpose. Belgium, Bulgaria, Croatia, the Czech Republic, Hungary, Luxembourg, the Netherlands, Poland, Romania, Slovakia, Slovenia and Switzerland get 45 days for tourism only. Thai citizens can visit Vietnam visa-free for up to 30 days (see Vietnam visa rules for Thai citizens), and US citizens need a visa except for stays of 30 days or less on Phu Quoc. If you're unsure, check your Vietnam visa needs.
Trip order decides which eVisa you need. Fly into Vietnam, out to Thailand and back again, and a single-entry eVisa won't cover the return. With Vietnam Visa by BDA, a one-month multiple-entry eVisa is $84 against $54 for single entry, $30 more, with the Vietnam Immigration stamp fee included (see our pricing). Vietnam Visa by BDA is a private company. We're not affiliated with the Vietnamese government, and if you apply yourself at evisa.gov.vn, you pay only the $25 single or $50 multiple-entry stamp fee.
Thailand's rules changed on September 15, 2026. The UK says visa-exempt visitors can stay up to 30 days, for tourism only, and visa-exempt entries through land borders are normally limited to two per calendar year. Canada lists the same 30 days for Canadians; other passports should check Thailand's own rules.
The arrival forms work differently too. Since May 1, 2025, every foreign national entering Thailand by air, land or sea has to complete a digital arrival card, within 3 days before arrival. Vietnam's Pre-arrival Information (PAI) is optional, can be submitted up to three days before you arrive and gives you a QR code to show on arrival. It's been piloted at Tan Son Nhat airport in Ho Chi Minh City since April 15, 2026, and Vietnam plans to roll it out to more airports, still on a voluntary basis.
⚠️ Only use prearrival.immigration.gov.vn for Vietnam's PAI. The Ministry of Public Security warns that fake PAI sites exist. PAI isn't a visa either: you still need an eVisa or a visa exemption.
A Few Parting Notes on the Numbers
We checked every rainfall and temperature figure in this guide against the long-term monthly averages the World Meteorological Organization publishes from each country's weather service. The Vietnam figures are 1991 to 2020 normals, Bangkok's cover 1961 to 1990, and the WMO lists no period for Chiang Mai, Phuket or Ko Samui.
Averages describe a typical year, not yours. In typhoon season, Canada advises travelers to be prepared to change travel plans on short notice. And sort the visa before the flights: it's the one part of a two-country trip that runs on someone else's working days.