If your tank is heavily planted and there is plenty of food for the loaches, and if your betta rests in wide leaves close to the surface you shouldn't have a problem. However if the betta rests on the bottom of the tank there may be a problem. I have never seen any where in recommendations that any loach makes a good tank mate for a betta. I don't think I would try this pairing. I know it seems that the loaches seem passive during the day but when the lights are off is when they search for food. and I would think they could very well mistake the slow moving long fins of a betta as a possible meal.
As I said I have never put a betta in with loaches so I would defer to others that know for sure. I have community tanks with these very interesting loaches in them and I do know that if any little fish is hurt by others in the tank the loaches do not hesitate to get rid of the body.