Baseline: routine vaccines up to date, plus hepatitis A, which the CDC recommends for unvaccinated travelers to Thailand and the wider region.
Then it depends on the trip: typhoid for rural stays and adventurous eating, Japanese encephalitis for long rural or outdoor exposure, and rabies pre-exposure for remote travel where post-bite care is far away. Malaria pills apply only to specific rural and forested areas, not the cities and beach hubs. Country lists differ, so a travel clinic visit 4 to 6 weeks before departure, working from the CDC's destination pages, is the real answer.
What to do
Common questions
What vaccines do I need for Southeast Asia?
The baseline is the same for the whole region, then it personalizes by country and travel style. Using the CDC's Thailand page as the regional template: make sure you are up to date on all routine vaccines before every trip, and hepatitis A is recommended for unvaccinated travelers one year and older, since it spreads through contaminated food and water across the region. After that it splits by itinerary. Typhoid vaccine comes up for travelers staying with local families, eating adventurously, or going to rural areas. Japanese encephalitis vaccine is for long stays or heavy rural and outdoor time in transmission zones. Rabies pre-exposure shots make sense for remote trekking, cycling tours, or animal-heavy trips, because the post-bite treatment is hard to find fast in rural areas. Country differences matter: dengue is vaccine-irrelevant for most tourists (bite prevention instead), while malaria pills apply only to specific rural and forested areas, not Bangkok or Bali's beach towns. The practical move is a travel clinic visit 4 to 6 weeks before departure with your actual itinerary, since Southeast Asia covers countries with meaningfully different lists, and the CDC destination pages give the per-country specifics your clinician will work from.