Muay thai is a martial art that can move extremely fast, and so the gear should not slow you down. The best muay thai gear straps on securely, is light and durable, and will not slow down the fighter while enhancing their capabilities. This is why you see buckles used rather than Velcro straps; the buckles are less likely to come off than the straps. This is also why plastic is used rather than metal or wood, which are heavier and bulkier.
This is also why you see the pads look smaller than other martial arts pads; even the pads must not slow down the fighter, and regular-sized pads would be a hindrance to most fighters. When you are looking for great fighting gear, make sure that it does not slow you down and that it fits securely for your best fights while wearing that gear.