Amparo, 25, fell short in the eyes of the judges. Two judges scored it for Le with scores of 113-111 and 117-111, while one judge gave it to Amparo 116-112.
After an impressive run this year, Amparo saw his streak end to five wins. He dropped to 11-4-1 with two knockouts.
The 29-year-old Le remained unbeaten with 6-0 with three knockouts.
On the other hand, John Michael Zulueta kept his Asian Boxing Federation light flyweight strap and his unbeaten record after a split draw with 18-year-old Thai prospect Suriya Kraimanee.
One judge gave it 96-94 for Zulueta, while the other judge saw the other 96-94 for Kraimanee. A third judge scored it a 95-95 deadlock.
Zulueta, ranked No. 14 by the WBA, is now 14-0-3 with seven knockouts, while Kraimanee logged his first career draw and is 4-2-1 with two knockouts.