Will ED Visa be denied after tourist visa has been denied?

I’ve been living in Thailand for a while, first at a mix of ED (two times 1-year) and tourist visas but I changed my passport twice because both are full of visa stamps.
My new passport has 6 single-entry tourist visas and the last one has a remark that reads:
“The holder of this passport travels to Thailand under a tourist visa several times, which may result in the refusal of a visa in the future”
My last tourist visa was denied right away in Vientiane, the lady at the table checked my passport and said too many tourist visas.
I went to one of the agents outside there and they helped me to get back into Thailand with a 30-day visa on arrival becauseI came with my Thai registered car.
The 30 days are almost due and immigration told me I can extend it another 30 days, but that’s just a very temporary solution.
I spoke with another agent near immigration and Ican apply for an ED visa for 1 year, paying a decent amount upfront, no strings attached.
HOWEVER,
How big is the chance that the Thai embassy in Laos will deny myED application?
(Once I pay the school, I’m pretty sure they won’t refund me if my visa gets denied).
The remark in my passport clearly says ‘a’ visa, it doesn’t explicitly say a tourist visa.