Morning from Mexico... I am a USA citizen    I need your help... Please. I want to stay in Thailand  90 days.. A little less  actually. On arrival I get a 30 day tourist stay? Then what? Or must I go to a Thai consul in Mexico before arriving? 

Providing they actually let you on the flight you can get a 30 day extension at immigration.

You really need a Visa for a stay of over 30 days.

Ok Thanks. Wow.. a trip to my local Thai Consul for a visa  :)

Yes, you want a single entry tourist visa (which right now is free) which will give you an initial 60-day stay in Thailand. This can be extended for a further 30 days (for 1,900 baht = about US$55) without leaving the country.

4 hours ago, 1happykamper said:

Ok Thanks. Wow.. a trip to my local Thai Consul for a visa  :)

You can apply at the embassy in Mexico City, or the honorary consulates in Monterrey or Guadalajara.

Info can be found here on embassy website: http://thailatinamerica.net/mexico/index.php/en/visas/who-needs-a-visa

The visa will be free if you apply on or before February 28th.