Is it worth visiting Thailand in April?

Yes, especially if you plan to participate in Songkran (Thai New Year) in mid-April. You will get wet, which is the best way to cool down, but be prepared for intense heat and high humidity.

Do I really need to avoid tuk-tuks?

In the hot season, yes. They offer no shade or air conditioning, and you end up breathing in exhaust fumes while stuck in stagnant heat. Use Grab or Bolt to hail a car with AC instead.

Staying cool in Thailand during the hot season

To survive Thailand's hot season (March–May), limit outdoor activities to before 10:00 AM and after 4:00 PM. Rely on air-conditioned malls for midday cooling and prioritize drinking two liters of water mixed with electrolyte powder daily.

Master the midday retreat. Do not plan walking tours or outdoor temples between 12:00 PM and 3:00 PM. Use this time to explore the city's vast air-conditioned shopping malls (like Siam Paragon in Bangkok) or retreat to your hotel room to rest during the peak UV hours.
Use public transit with climate control. Opt for the BTS Skytrain or MRT Subway in Bangkok. These are heavily air-conditioned and vastly more comfortable than sitting in gridlocked traffic inside a hot taxi or tuk-tuk during the afternoon.
Upgrade your hydration. Plain water isn't enough when temperatures hit 40°C (104°F). Buy 'Royal-D' or 'Dech' electrolyte sachets at any 7-Eleven. Mix one packet into a 500ml bottle of water twice a day to replace salts lost through heavy sweating.
Dress for the humidity. Avoid synthetic fabrics. Wear loose, thin linen or technical moisture-wicking fabrics. Carry a small hand fan or a portable neck fan; the constant airflow helps significantly with evaporation cooling.

Is it worth visiting Thailand in April?: Yes, especially if you plan to participate in Songkran (Thai New Year) in mid-April. You will get wet, which is the best way to cool down, but be prepared for intense heat and high humidity.
Do I really need to avoid tuk-tuks?: In the hot season, yes. They offer no shade or air conditioning, and you end up breathing in exhaust fumes while stuck in stagnant heat. Use Grab or Bolt to hail a car with AC instead.