You mean complementary transit tour ? I don't think there's any. But there's tourist info center at the arrival floor that you can check it out.

But it's rather easy to get to town from the airport by airport link (it's a sky train but the Thais would refer to it as "airport link". The word sky train implies another system (BTS) which connect within BKK city)

You can take airport link to Phyathai and connect to BTS to Paragon, Terminal 21, the famous Jatuchak market (if you're there on the weekend)

You can also take airport link to Makkasan and connect to MRT subway system to Hua Lam Pong which is a walkable distance to China Town.

The major tourist sites e.g. Grand Palace, Marble temple are not reachable by BTS or MRT. You will need to take taxi or tuktuk and may run a risk of getting a drivers who will try to convince you to tailors, souvenir shops or seafood restaurant (with the premium prices). So take that into consideration when planning your time.

Have fun.