First, read the English article below.

The ideal time to repot an orchid is right after it finishes flowering, when it begins to produce new growth. However, you don't need to repot your orchid every time this happens; rather it should be done no more frequently than every 18 - 24 months. If you're not sure when your orchid was last repotted, and it seems to be growing out of its pot, yours may be overdue for a repotting. Take a look at your orchid for the following signs to know if it's ready to be repotted:   Several roots are growing over the pot. If you see many roots - not just one or two - dangling over the pot, your orchid needs more room, and it's time to move it to a bigger space. Some of the roots are rotting. If they seem soggy, and the potting material is no longer draining properly, you'll need to repot the orchid. The plant is growing over the edge of the pot. If the bulk of the plant is leaning way over the edge, it needs more space. Being overzealous with orchid repotting can throw off the plant's growing cycle. An orchid should only be repotted if the above symptoms are evident. If it looks to be healthy and well contained in its current pot, put off repotting for another year. It's better for the orchid to get a little overcrowded than to be repotted too soon. Now that you know it's time to repot your orchid, it's important to figure out the right type of potting material to use. Many orchids used as house plants are epiphytic, rather than terrestrial, meaning they don't grow in soil. These types of orchids will die if you repot them in regular potting soil.   A combination of fir bark, sphagnum moss, charcoal and coconut husks is appropriate for many orchid genera. Most common orchids will do well with this mixture: 4 parts fir bark or coconut husks 1 part medium charcoal 1 part perlite   If you're not sure exactly what kind of orchid you have, packaged potting mix for orchids is a safe bet for most epiphytic orchids. It's available at many nurseries and home and garden centers. If you have a terrestrial orchid, you'll need soil... 

Now, please write a short abstract for it in Vietnamese. Abstract:
Xác định thời điểm cần thay chậu. Không thay chậu cho lan trừ khi thực sự cần thiết. Tìm loại giá thể thích hợp. Xác định kích cỡ chậu cần dùng.