The Bangkok HP is one of the better ones, reminds me of a Regency with a smaller pool but less service, especially luggage. I haven't stayed there, but a friend of mine has many times, as Globalist, so they always gave him a great room. Maybe the base rooms are just so-so. On the other hand, all of the The Bangkok HIX's have tiny rooms with a marginal breakfast spread, especially the Suk 11 one which is also a real pain to get to as it's all the way down Suk 11 and the taxi mafia are out in force, They do have a shuttle but it won't help you from the Sukhumvit area unless you call them to pick you up. Taxi drivers have told me THB200 many times. Siam is OK with a little larger room size, but very noisy as the National Stadium BTS station is just nearby and they "turn" the train around there, so you're too close, but they run until midnight. The Sathon one is OK only due to it being closer to the Chong Nonsi BTS stop without all the train noise, but the rooms are tiny and the breakfast marginal. The street food is good though just around there.
The best HIX properties are in China: HIX Zhabei near the Shanghai north train station, where they always UPG'd me to a real suite and have a great breakfast, just stay away from the buffet items and stick to the egg/noodle/Chinese pancake stations; and the Nantong Downtown one which has a partial river view from the higher floors, with larger rooms and a (somewhat) edible breakfast. Both were dirt cheap, but decent.