I normally rent from Budget due to competitive rates and my perceived receipt of better service from them as compared to Avis. They also allow free one way rental dropoff for rentals of, I believe, 5 or more days. Their network is fairly extensive covering most airports.

Often they have specials for those who possess certain branded credit cards as well. They also have excellent regional maps that the other agencies do not.

The reason that I mention no drop off fees on longer rentals is that I will not drive in Bangkok not because of the traffic but because I do not read Thai and much signage is in Thai. Construction and detours in the city along with chaotic traffic make finding one's way a challenge should you become lost due to a misturn.

Some less traveled areas include the area north of Chiang Rai, the golden triangle, Chaing Mai to Chaing Rai via Fong. Phuket to Hua Hin via Ranong and Chumpon, Isaan north of Ubon Ratchithani to the Mekong. The back roads between Krabi and Khao Lak. Many of these areas are jungled and have some spectacular scenery. Places to stay may be difficult to find but they are available by using www.google.com.