Well, I was about to come back to edit my former post when I saw this post.
I was reminded of you telling the year being around 1900s so, it is likely to be one of the palaces within the big compound of Dusit Palace originally built in the reign of King Rama V (the location that includes Anantasamakhom Throne Hall for instance). There are a lot of small palaces inside and most of them were built for female royalties starting from the Queen (even now, the Queen Mother (King Rama X's) resides here), Royal Consorts, Royal Concubines and more.
The Belgian doctor, was his name Dr. Eugene Reytter? He had served the King's as one of the team of doctors for around 17 years, starting from 1895. He later was granted a noble title as 'Praya'.
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