Will the hotel front desk really receive my laundry?
Yes, almost always. Bangkok hotels — from $30/night Khao San hostels to luxury 5-star Sathorn properties — routinely receive guest laundry from third-party services. They've done it thousands of times. You don't need to ask permission, just tell reception when checking in or before pickup: 'a laundry service is coming for my dirty laundry around 4pm — they'll ask for [your name].' Reception will hold the bag for you on return. The only hotels that actively refuse: small bed-and-breakfasts run by a single owner who isn't always at reception (rare in Bangkok).