I have stayed there a few times over the years, most recently last August.  It is 100% LB friendly and there is no guest charge, just ensure that your advance reservation is for two guests. Any security guards you see will just smile and wave at you and your LB. It has entrances on both Soi 2 and Soi 4. Soi 2 entrance is the lobby and Soi 4 entrance is through a small parking garage. The smart move is always depart the hotel thru the Soi 4 entrance and then return through the Soi 2 entrance. Soi 2 has very little traffic compared to Soi 4 and if you utilize taxis or tuk tuks, it is much faster using 2.  They have a large rooftop pool that has no shadows and there are always plenty of loungers available. If you walk across the skybridge to the other hotel tower, you will find a nice rooftop garden that attracts loads of hummingbirds. It's a pleasant surprise and a real gem.  I have never tried their restaurant, but a couple of minutes away on Soi 4 are Swan and the Dawin hotel's restaurant, both of them modest but outstanding places that punch above their weight. The Dawin's restaurant is directly across the street from Why Not, so while you eat your dinner you can check out the available girls at WN.  It's not fancy, but it is spotlessly clean, quiet and the rooms are large. It's good value for the money, less expensive than similar hotels like Adelphi Suites but its location is on the periphery of the red light district and the LB bars take a bit more time to travel to. 

Nope ... directly on https://all.accor.com

Agoda?

I've booked (a while ago alreafy) the Mercure for my upcoming trip, end of March. Costs about 100 Euro (87 GBP) per night 

Should anyone be thinking of a lower Sukhumvit Hotel booking it seems as of 1st March the prices are falling. I have just booked The Mercure at £370 inclusive of tax for 5 nights, last week this same booking was pushing £600.