Let $P(x\_1, y\_1)$ be any point on the hyperbola, which satisfies $\frac{x\_1^{2}}{4} - \frac{y\_1^{2}}{12} = 1$. The equations of the two asymptotes are $\sqrt{3}x - y = 0$ and $\sqrt{3}x + y = 0$.

The distances from point $P(x\_1, y\_1)$ to these asymptotes are given by $\frac{\left| \sqrt{3}x\_1 - y\_1 \right|}{2}$ and $\frac{\left| \sqrt{3}x\_1 + y\_1 \right|}{2}$, respectively.

Multiplying these distances, we obtain $\frac{\left| \sqrt{3}x\_1 - y\_1 \right|}{2} \cdot \frac{\left| \sqrt{3}x\_1 + y\_1 \right|}{2} = \frac{3x\_1^{2} - y\_1^{2}}{4} = 3$.

Therefore, the product of distances from point $P$ to the hyperbola's asymptotes is a constant, $3$.

Hence, the answer is $\boxed{3}$.

To solve this problem, we first assumed $P(x\_1, y\_1)$ to be any point on the hyperbola. Then, we determined the equations of the asymptotes and used the formula for the distance from a point to a line to express the distances of $P(x\_1, y\_1)$ from the asymptotes. Finally, we multiplied these distances and simplified the expression to obtain the answer.

This problem primarily assesses understanding of the basic properties of a hyperbola, such as its asymptote equations, and the application of the formula for the distance from a point to a line.