Renthub question

I visit Bangkok 2-3 times a year for a month and usually use AirBnB for my accommodation. As the AirBnB prices increased I was looking for alternatives and found renthub.in.th. Most of the fully furnished condos are with minimum 1 year contracts but some of the landlords are willing to rent out on monthly or weekly basis. Does anybody have experience with Renthub? Are the agents and landlords reliable there? Are the short-term agreements "black market deals" or do you get a normal rental contract? (budget is around 50k a month and location Siam, Ploenchit, or Asok)

Thanks