The Ambassador Transit Hotel (I haven't stayed in the one in T2, but that shouldn't matter) gives you a room with an ensuite private toilet, shower, and sink. There's a small desk and desk chair, a place for a suitcase, a few hooks/hangers for clothes, and a color TV with remote having only a small choice of channels, IIRC the only English option is Channel News Asia, not CNN etc. You'll also have a small kettle for heating water, two cups, instant coffee, teabags, a packaged cookie/biscuit or two, and other supplies. The bathroom has basic toiletries (soap, shampoo, shower cap, facial tissues, etc.) and IIRC a hairdryer. Of course the hotel supplies towels, but there might not be washcloths in the bathroom. IIRC there's free wifi and a phone; they do wakeup calls. I don't remember an alarm clock in the room but you might be able to set an alarm in the TV.

There might still be a few budget rooms in T1/T2 without private toilet and shower facilities.

In T3, the rooms seem fresh, modern, and stylish in a minimalist way, but many of them do not have windows. [There is AC that you control.] The single rooms that I've seen have one double or queen sized bed.

The lobby mostly consists of a check in counter. IIRC there's a computer and printer for guests to use.

I don't recall whether there's free bottled water in the rooms, but my guess would be yes.