Is it too risky to travel to Thailand again on a Tourist Visa before applying for a Marriage Visa?

One option maybe a airport VIP service, and I say this because even with a applied and approved tourist visa and IO can still say no, price of the VIP service is between 2-8k baht depending on your passport history, basically and IO would come and get you from one of the big doors close to the immigration ramp and walk you through and stamp you in no questions asked and then they go and get a nice cup of tea....also I would advise that the cash you have on you is in baht and not pounds because if you do get pulled aside to the questions area, your only hope would be to pass the IO your passport with the cash in it so they can take a photo of it and also show their supervisor it, as I understand it, while they look at it they may have a cup of tea and let you in, if you play nice that is, if they do say no then you would get taken to the inner guts of the airport and told very little until an airline rep turns up to say you need to book a flight back to UK asap, cannot pop to Vietnam and come back in a few days, and then you will get taken to the detention centre in the basement where you will stay until your flight and you have to pay 1070 baht a night, you do get food and water, but there is no paper or bum gun in the toilet, and then when your flight is happening they will collect you and walk you through the airport and they keep your passport for the whole thing, you only get it back from and IO at your destination and your first on the plane and last off and taken by ground crew to the IO where you get more questions, if it's UK you should be ok, but for me when I was denied it was DaNang airport and I did wonder what would happen if they said no, all this happening to me is why I choose to use the VIP option because like I say an IO can say no to any visa if they want, playing their game is a little scary but it works, anyway good luck with whatever you decide to do, but you may want to use VIP for Aug and Oct as they as close together.....oh and the reason given to me for my denied entry was returning for a third time within a 6 month window, it's true I was but I had no overstays or anything else dodgy, I have heard from many people they really are asking more questions and a few friends over 50 have been questioned as to why they don't have a retirement visa.....

You could just get a relevant visa😀

If they stop you in August then you will have a black mark on your Immigration file. Up to the individual IO but it could make coming back in October difficult. Better to be safe and get a proper visa. They are really cracking down on tourists. I was changing from OA to O and was questioned as I had to come in as a tourist just to get the O visa changeover

If you're worried get your Non-O before travelling in August then get a re-entry permit for your return in October to apply for your 12 month extension (take the 60 day Visit Thai Family extension if necessary)