That requirement is not valid anymore. It was in the past though..
Anyway, I don't think you should have any problem coming for a short visit without visa and get your 30 days visa + Extend your stay 15 days at a time using the border crossings.
If you would like to stay longer you will need to issue a proper Thai visa and you should be able to do it prior your arrival in the Thai consulate in your home country.
*There is no limit on the times you can do border crossings 15 days visa run (Thai visa laws of today. Can change anytime) however it is not a way I would recommend to do so as its not Financially lucrative and they might tell you after several times doing it just to go and get a visa.
Anyhow, if you DID came without a visa you can issue a proper visa in a neighbouring countries around Thailand. (Laos is the closest).
Give us more details and we can help.
Buriram Expats Visa Run Service:Tel: 081-0704750
Email: info@buriramexpats.com