Depending on your nationality and the location of the nearest Thai Embassy/Consulate, a 3 month business visa is relatively easy and not expensive. You must have the most senior official of the business that is requesting the visa sign the letter, but in most cases this is the applicant themselves.

However, they won't be asking you any questions at the immigration counter. If you qualify for a 30 day entry without a visa, they will just stamp you in.

Neither way is complicated. The visa just takes a bit of planning.