I am an Indian passport holder. I visit Thailand 3-4 times a year and stay less than 10 days a trip.

I am granted a 15 days visa at Suvarnabhumi airport on arrival.

Are there limitations on the number of times i can be issued such visa (15day/tourist) on arrival?

There is much discussion about recent enforcement of the existing visa-free entry regulations which applies to those nationalities who qualify for a 30-day permission to stay (not same as visa on arrival) and particularly their back-to-back 'visa runs' over a nearby land border.

I assume that your visa-on-arrival requires you to apply and submit the application at a desk BEFORE the main passport control desks in the Immigration/baggage hall?

I would assume that since you always arrive and depart by air, your visits are relatively short and the periods between them may be 2-3 months (?), you should not expect any extra scrutiny as your frequent but not excessive visits do actually fit that of a typical tourist.