Oneworld member Qatar Airways has currently discounted round-trip flights from Prague to Thailand. Round-trip fares start at €525 (~CZK 12,715) to Bangkok or at €529 (~CZK 12,812) to Phuket, with 25 kg of checked luggage included.
On most dates to Phuket, a 9-hour layover in Doha is required on the outbound leg (and 6 hours on the return). Connections to Bangkok generally offer shorter transfer times.
Available dates run through June 2027 and can be searched on Google Flights, where you can also filter by layover duration.