Last 2 times I struggled to eat anything other than toast and brought real food back in over a few days.

I have used antibiotics both times previously as 2 days and imodium were just not doing the job, what I hope to be able to do is avoid the symptoms from day 1

I had a Thai doctor prescribe Norfloxacin 400 some years ago and when I asked a pharmacist for this time ago he recommended Ciprofloxacin as this was a more potent antibiotic for more persistent cases.

With the changes in time zone, more boozing, different food etc stomach issues are not uncommon but avoid antibiotics unless it really is persistent.

Another good option are charcoal tablets you can pick up from 7/11 which is helpful to settle your stomach after a rough night!

Sometimes ciproflaxacin will clear prolonged symptoms at least for me.  Cipro was first recommended and prescribed to me by my doctor ahead of my first trip (along with a typhoid vaccine).  I usually don't have issues however over the three years that I lived in LoS it occasionally happened.  When it did cipro almost always did the trick. During my three years in LoS I also learned to be very careful with dairy products.  As anyone who has visited a Thai market has probably noticed, Thai people have very casual attitudes when it comes to refrigerating food.  On several occasions I've had GI issues after eating cheeses, yogurt etc from Tops, Big C etc. - places you'd think would be safe.  My take was that just because something is cold in the deli case doesn't mean it didn't sit out on the loading dock in 90+ degree heat for a few hours.

Well done steaks are a crime against humanity!