How can I extend my stay in Thailand after 180 days on a DTV visa?

I have just being approved (DTV) by the Spanish Embassy.

My experience has been as follows:

1. Bank Statements: I provided bank statements for the last 6 months for at least 500k baths during the period.

1. Payroll: I submitted my last 2 payrolls.

1. Employment Contract: Although I mentioned that I was going to work on projects as the clients demands and was not on the payroll, the company provided an official letter confirming this situation.

1. Purpose of Visit: They asked for a letter explaining what I would be doing in Thailand. Since I work for a Corporate Incentive Travel agency, I explained that my goal was to get to know the country on a firsthand to recommend Thailand as a destination to our clients.

1. Additional Documents: I also included the rental contract of the house we had rented + health insurance by AXA that my husband and I obtained + medical certificate confirming that we do not have any diseases required for the OA non-immigrant visa, which my husband is also applying for at the same time.

Uffff so release with the news.

Question; My purpose is to stay for 8 months in Koh Samui, so to extend for 2 more months (6+2), should I change my visa after the 180 days? Should I stay as a tourist? Thanks in advance