This is a Visa and Work permit for Non Profit Organization. You will be required to engage in volunteer activities with the charity (primarily assisting disadvantaged children). This will be in the form of
Volunteer work for the charity:
* Cooking and preparing food
* Delivery and serving food packages in local schools and Hill-Tribe communities
Visa application can be applied either at your local Thai embassy, or within Bangkok. You sound like you are following the latter way. Did you check with your local Thai embassy?
Entering on a tourist visa and convert visa isn’t an issue at all