Trat (TDX) is a smaller airport in Thailand. The one and only destination from here is Bangkok (BKK) with Bangkok Airways where you can fly 7 days a week.
If you are in need of a rental car, there are several options at TDX.
If you are arriving at Trat and want to go to the city, you have several options. You can take a bus, a taxi, or a rental car. The bus is the cheapest and most convenient option, as it runs frequently. The taxi is more expensive and may take longer depending on the traffic. The rental car gives you more flexibility, but you have to pay for parking and fuel.