I've been coming to Bangkok pretty regularly since the late 1990s. I've stayed in every kind of place, from $10-a-night hostels to suites at The Four Seasons. I'm always looking for properties that offer the best value for money - dollars and pounds go a long way here, especially in the off season, but it's still well worth looking around for a bargain.
I'm currently staying here at Citrus Soi 11 in Sukhumvit. I'm not being hosted, and I don't have any obligations to or affiliations with the hotel. I'd argue that this is one of the best value hotels in the city at the moment, and you can likely find rooms for around $40/£35 per night or so at the right time of year (Bangkok is, of course, subject to the same price fluctuations as any large city regarding festivals, conventions, etc).
Citrus Soi 11 (there are other Citrus properties around town) is a five minute walk from Nana Sky Train station on Sukhumvit Road, and so it's immediately well located for public transportation, nightlife and shopping. The MRT (subway) isn't much further. It's off the busy main drag of Soi 11, a couple of corners snaking round off the hectic street on a quieter stretch. I'm writing this at rush hour (which is no joke in Bangkok) and I can't hear any traffic.
It's a contemporary design, understated with clean lines and light wood finishes - it's not trying too hard, the way some gaudy three or four star hotels can. The interiors are modern; tasteful, even.
I'm in a 'Classy' room, which is a level above the entry-level 'Cosy' rooms. It's 28sqm (300sqft). There's not much between them beyond the floor space. The large windows and light wooden floors give it a bight, airy feel, and there's most things you might need. Included is: daily bottled drinking water, tea and coffee in the room, a mini fridge, flannel robes, slippers and a safe large enough for your laptop and valuables. There's free wifi and a good-sized desk/work space.
The onsite restaurant, Munch, has a very decent breakfast buffet with cooked western favourites (eggs, sausages, hash browns, baked beans, etc). I'm on my second week here and I'm not tired of it yet. They vary things a little every day, especially the curries and soups, and there's always lots of fresh fruit, squeezed juices, etc. It's also open for lunch and you can book rooms with breakfast included (otherwise it's 199bht/US$6/GBP£5 for all you can eat). They also operate as a coffee shop, and they stay open for lunch, with a good choice of casual options, including Thai curries.
The only downside is that there's no swimming pool, but the hotel does have a perfectly fine gym and a rooftop with good views over the city. There are dozens of restaurants within a minute's walk, laundry services, Thai massage, grocery stores, you name it. The canal is also a couple of minutes away, with the regular boat taxis being an underrated way to get around in Bangkok.
It's also a full service hotel, with lobby attendants, a tour concierge, drinks (including beer) and snacks available at the front desk, cheery helpful staff. There are taxis, tuk-tuks and motorcycle taxis all right outside the property.
Honestly, for a clean, contemporary hotel with most things that you could need - including a great location - I haven't found anywhere lately that measures up to the value here.
Citrus Sukhumvit 11 by Compass Hospitality