I am looking to leave a suitcase in Bangkok for a weekend, preferably near the northern bus station. Does anyone know how or where to do this and how much it may cost? I heard there may be a place in the northern bus station?

Will you be staying in a hotel in Bangkok? If so, check with the hotel and see if they will store a suitcase for you. Last year, I stayed in the Amora Neoluxe Suites off of Sukhumvit and they stored a suitcase for me while I took a 3 day trip to Kanchanaburi.

In the Northern Bus station, when you enter the main door, you will see a 7-11 INSIDE the terminal on your left. walk to your left there going towards the food area. Immediately on the right near the first set of doors is a small convenience shop and left baggage is to the right of that.

Not very well marked and very untidy.

The previous suggestion to see if your hotel has a baggage room is a better choice. Most hotels do.

Yup my friend used to leave had suitcase at the hotel. Another friend used to leave his golf clubs there full time. He would come to Thailand every 2-3 months but not an issue they held them all year long at no cost.

Almost any larger hotel will have a luggage storage room. TIP the bellboys and you'll be well taken care of no matter how long you want to leave it there .