An irregular sampling of regular waveform based true random number generator(TRNG) utilizing a tetrahedral oscillator as entropy source is proposed. The tetrahedral oscillator is composed of multiple nested rings which increases entropy due to metastability. By integrating tetrahedral oscillator with irregular sampling method, the proposed RNG is faster and more robust to external interference attacks than regular sampling of tetrahedral oscillator, it uses much less hardware resources than regular ring oscillator based RNGs. In total, 5 tetrahedral oscillators are used as the entropy source and they are combined with an XOR gate. This XOR output is used to sample a faster regular clock, which should have a duty cycle as close to 50% as possible, to generate the random bit. The randomness of the bit stream was proved with National Institute of Standard and Technology (NIST) 800-22 Test Suites. The proposed design uses 93 LUTs and 14 FFs while consuming 100mW of power and having a throughput of 1.7MHz. The speed is 17 times faster than regular sampling of tetrahedral and the resource usage is 16 times lower than regular ring oscillator based RNG designs.