I stayed some years ago as Wyndham Diamond and got free lounge access and suite upgrade.
I now emailed them again earlier this week, what are the benefits and it seems like Diamonds still get suite upgrades, but no free lounge access anymore.
They also said:
According to your request for Benefit as of Platinum or Diamond , in case make a booking under go free the package do not included breakfast & Club benefit , in this case there will be additional charge as below details.,
Breakfast: THB 790.- per person per day
After noon tea: THB 650.- per person per day
Evening Cocktails : 950.- per person per day
Total 2390.- THB per person per day
I also noticed that on their own hotel website they sell rooms with modest surcharge for lounge access and asked if booking via their website I'd also earn Wyndham points or get benefits, but was told "no". Only bookings via main Wyndham website or app, but not the website of the hotel or their reservations team.
I think the rooms are quite similar. I'd go for riverview rather than the pool view.