Just because they don't ask... but they can if they want to... see 4 below.
Be from an approved country.
Be visiting Thailand strictly for tourism.
Hold a genuine passport with a valid expiry of over 6 months.
Can provide a valid address in Thailand on entry that can be verified. This address can be a hotel or an apartment.
Must have a confirmed return ticket exiting Thailand within 30 days. Open tickets do not qualify. Traveling overland by train, bus, etc to Cambodia, Laos, Malaysia (including en route to Singapore), Myanmar, etc is not accepted as proof of exiting Thailand.**
Provide proof of funds of at least 10,000 THB for single travelers, or 20,000 THB per family during your stay in Thailand.