Just checked out earlier today from another stay. No upgrade this time at all, not even to corner room. I talked with GM and it seems like only way to get a suite even as Ambassador is paying cash as over 50% guests are Platinum and above.

I don't know about that Afternoon tea, but I saw some people having more classical afternoon tea "tower" setup on some of the days.According to their pricelist that 60min massage is worth 1500THB.

Even if you don't stay at LM, you can consider enjoying their breakfast, which is these days only 360THB net midweek.

Regarding using the hotel credits - I used some at the Rolling Ribs (https://www.rollingribsbangkok.com/) on ground floor, which is having nice BBQ selections.Better book a table on Fri/Sat evenings as it can get quite busy.