Visa exempt can only be for tourist reasons, not for work or meetings so you must always put it is for tourist reasons. Make sure that you follow the directions on your consulate website for filling out the COE and upload the necessary documents.
If your passport nationality qualified for visa exempt entry, you can apply for a certificate of entry (COE) from the Thai consulate based on visa exempt qualification. Your local consulate website should give you info on how. If your nationality had Visa On Arrival qualification for Thailand instead, then that is currently not possible and you will need to apply for a visa as well as the COE.