What should I do if my tourist visa application was denied at the border due to a previous stamp error?

Ok I can only try and explain what I think has happened.. So I came out to Savannakhet 2 months ago was refused a setv on the minor technicality of proof of funds, fair enough the guy said Everything is ok just show funds..Just to went back to Thailand on exempt as I have not used my 2 calendar year land crossing, all good arrived today with copious amounts of statements in all shapes and sizes lol..the guy took one look at the passport and said I can't apply for a tourist visa again didn't even look at the docs I was told to bring..I asked and asked something wasn't right he couldn't give me a straight answer... I rechecked my passport and seen I had and extra used stamp on a old setv... they made. A mistake somewhere maybe on my last entry to Thailand and he as not willing to deal with it..or something else..? Anyone have the slightest idea what's going on here.i will post a picture of what I think could be an issue ...

The issue now is I have used my 2 land crossings through no fault of trying to get a visa..got caught in the mess when Vientiane started the online bookings,, I have been out of the game for a bit as I went back to U.K for a bit..got a tourist visa easy in the U.K. just used the online service so was...happy...all responses very welcome as I'm lost,On the plus side I still have thirty days in Laos to find a solution... cheers sorry for the long essay..really need help.. I was offered to exchange $s for a transit visa but I'm not willing for something like this, is a transit only 30 days anyway?