Suvarnabhumi International Airport.
Visa on arrival is a waste of time and energy. Most flights from Kolkata arrive at early hours of the morning and there is only one counter open. Better to take it beforehand, as it costs less and makes the transit through immigration faster. Note, that you get to collect your luggage only after passing immigration. The area outside the carousels contains a row of SIM shops. Take an unlimited data SIM for 7 days. The different rates are mentioned on the counter.
There are stores at the airport that sell Nestle bottled water. Do not buy the more expensive varieties. For cheap food, buy some bread and cheese available at the stores and eat your fill. The Flights to Phuket are very cheap but what they don't tell you is that they allow only hand baggage. Luggage has to be purchased separately. The rates are 743 bahts but you can get a discount if you buy it both ways. Use only if the return flight is of same airline. It costs 986 Bahts then, which is steep.