You may have had the experience of gaining weight because you ate too many snacks and/or the wrong types of snacks. That can certainly happen. It's awfully easy to polish off a bag of potato chips, and who hasn't abused the office candy jar? However, snacks can be a healthy part of your diet, and there is no reason why snacks need to trigger your acid reflux.
A huge benefit of healthy snacking is that it keeps your blood sugar stable, and that stability will make you less likely to overeat. Why is that important? Because eating too much puts excessive pressure on the lower esophageal sphincter (LES), and when that happens, acid reflux becomes much more likely.
To keep yourself from getting famished and then overeating, try to eat something at least every four hours. Some people need to eat more often.
You have many reflux-friendly snacks to choose from. Consider any of the following, and several others. Basically, as long as the snack doesn't include triggers such as citrus, chocolate, chilies, tomato, garlic, onion, and high unhealthy fat content (lard, shortening), you'll probably be okay.
Non-citrus fruits
Crackers with any type of nut butter
Raw vegetables with dip or hummus
Baked chips
Edamame
Pretzels
Nuts (don't eat more than a handful though — nuts are high in fat, and having too much fat may trigger reflux)
Half an avocado and some corn chips (avocados are high in fat, but it's a healthy fat — still, don't overdo it)
Baked chicken strips (or any small quantity of lean meat, besides red meat)
Oatmeal or high-fiber cereal
A baked potato, sweet potato, or yam
Any type of grain
Rice cakes
Granola bars
Salad
Half a bagel
Lowfat dairy, such as lowfat cottage cheese with vegetables or crackers or fruit
A hard-boiled egg
A veggie or fruit (non-citrus) smoothie
Any food can be a snack as long as you keep the quantity small. So, if you have a favorite reflux-friendly meal, such as a burrito of refried beans, avocado, and rice, cut that leftover burrito in thirds, and one of those sections will make a fine snack later on.
Snacking will help keep you satisfied so that you don't get monstrously hungry and overeat at meals, which is all the more reason to engage in some modest reflux-friendly snacking throughout the day. Keep healthy snacks at work or school, and maybe even in the car, and that way you'll have good choices around when you're in a hurry or any other type of non-ideal circumstance.