Great water park but food allergen handling poor

If you love water parks you’ll love Siam park. I do want to say we arrived at 9am and by the time we got into the park through the gates at 9:15am all the fast passes were sold out…everywhere. None at any of the shops or kiosks - it was quite unbelievable. 1 teen of our party has autism and used the accessibility desk to get 2 fast passes (one for him and one for a guardian). Our plan was for the rest of our family to buy fast passes so we could all remain together. Unfortunately it meant our family split up for half the day which ruined the experience for me personally - so my advice if you plan to do what we had planned is to discuss how your family will handle only 2 of you having a fast pass and the rest of you slumming it queuing without the others. Food allergen wise Siam park is bad. My son has a life threatening egg allergy. I showed the chefs a translation card and my sons epipens. I got shown the food allergen matrix - a great start I thought. So I picked up my son a smash burger which was meant to be egg free according to the matrix. I got to the till and checked inside the burger when I could put my tray down. It was lathered in mayonnaise. I then had to get back through the queues and explain to the chef who made my son a plain burger. After paying, my son then pointed out back at the table, it was in a brioche bun (not egg free). I took it back and was told oh it doesn’t have egg in it. I pointed out the bun. And was told ALL the bread in the food has egg. So that could have been an anaphylactic reaction and trip to hospital had my son not pointed out the bun. So my advice if you have a severe food allergy, take your own food. I wouldn’t risk it.