So I got a 2way ticket in and out from bangkok for 30 days> but I'm traveling to phuket today and just bought my ticket (one way ticket). Will I need a ticket back to bangkok in order to travel to phuket or no? Can I just tell them that I'm going to buy one out of thailand once I get to phuket?

Once you are in the country you can travel and go anywhere you want with no restrictions. Tickets out and etc are only required for entering the country.

Phuket is in Thailand. Or have I missed something (in your post)???

I am unclear as to your question. Are you currently in Thailand? If not, and planning to enter visa exempt, the airline may want you to have a ticket exiting Thailand within 30 days before they will let you board. If you are currently in Thailand, domestic flights will not reset your permission to stay date. If you wish to extend your stay without leaving Thailand, you can get a 30-day extension from an immigration office in Bangkok or Phucket for 1,900 baht.

so if I get a 60 day visa by doing a border run would I be able to extend my return flight ticket or no?

also ubonjoe answered my original question so yea thanks for that, right now Im planning on going to phuket then doing a border run and hopefuly getting an extra 60 days on top of what I have now, so would I then be able to extend my return ticket?

The only time you will be asked for a ticket out of the country is to board your flight to here from wherever your are.

You will not be asked for it at a border crossing or immigration to get a 30 day extension.

You can change the date for your return at any time after you are in the country.

Not sure what you mean by "border run." You must visit a consulate or embassy in a foreign country to get a 60-day tourist visa. If you mean just jumping over the border to get another 30-day visa exempt entry and then extending it for 30 days in-country, you could do that to get 60 days.