This research investigated the feasibility of biodegrading plastic waste from municipal solid waste using potential microorganisms isolated from a petroleum oil wastewater treatment pond. Solid waste, specifically opaque and transparent plastic containers, was collected from a dumpster in Saensuk Municipality, Chonburi, Thailand, and cut into three sizes: 3 × , 4 × 4, and 5 × 5 cm. Each piece was weighed, with five pieces of each type (opaque and transparent) placed into jars along with other solid waste to make a total of 200 g per jar. The experimental setup included groups without microbial addition and groups with AS1, AS4, R13, R15, and AS4 + R15 cultures, incubated at room temperature (average 35 ℃). Size measurements and microscopic observations were conducted every 3 days for 30 days. Among the transparent plastic samples, the highest size reductions for all three sizes (3 × 3, 4 × 4, and 5 × 5 cm) were observed with AS1, AS4 + R15, and AS4. For opaque plastic, the highest size reductions were seen with AS4 + R15, R15, and R15, respectively. Microscopic examination revealed edge degradation in both types of plastic across all sizes when exposed to AS1, AS4, R13, and AS4 + R1, consistent with observed size changes. After 30 days, the waste was weighed, showing that R13 and R15 caused the most significant weight loss. Combustion tests on the decomposed waste indicated that the non-microbe group had the highest combustion temperature, reaching 745 ℃, and the longest burn duration. The AS4-treated sample had the shortest burn time at 6.14 min, while the waste without microorganisms left the least ash, at 23.42 g. Microbiological analysis identified AS1, AS4, and R15 as Enterococcus sp., and R13 as Bacillus sp. Genetic studies of these microorganisms will be conducted in future research.