Here’s a list of highly effective mosquito-repelling plants that are easily available and can be planted in Southeast Asia, ranked based on their effectiveness:

### 1. **Citronella (Cymbopogon nardus)**
  - **Effectiveness:** Very High
  - **Why:** Citronella is well-known for its strong aroma, which is effective in repelling mosquitoes. It is one of the most common ingredients in mosquito repellents.
  - **Growth:** Easy to grow in Southeast Asia’s warm and humid climate.
  - **Care:** Prefers full sun and well-drained soil.

### 2. **Lemongrass (Cymbopogon citratus)**
  - **Effectiveness:** High
  - **Why:** Similar to citronella, lemongrass contains citronella oil, making it an effective natural mosquito repellent.
  - **Growth:** Thrives in tropical climates, requiring a warm environment with plenty of sun and water.
  - **Care:** Needs regular watering and well-drained soil.

### 3. **Lavender (Lavandula spp.)**
  - **Effectiveness:** High
  - **Why:** Lavender contains linalool, which mosquitoes dislike. It’s often used in oils and sprays.
  - **Growth:** Needs a lot of sunlight and can be grown in pots or garden beds.
  - **Care:** Requires well-drained soil and moderate watering.

### 4. **Basil (Ocimum basilicum)**
  - **Effectiveness:** Medium-High
  - **Why:** The smell of basil, especially the Thai basil variety, repels mosquitoes. The plant’s essential oils are strong enough to act as a deterrent.
  - **Growth:** Grows well in Southeast Asia’s tropical environment, but needs regular care and protection from strong winds.
  - **Care:** Needs full sun and regular watering.

### 5. **Marigold (Tagetes spp.)**
  - **Effectiveness:** Medium
  - **Why:** Marigold flowers contain pyrethrum, which is used in many insect repellents. The scent helps to deter mosquitoes and other pests.
  - **Growth:** Easy to grow in Southeast Asia and can bloom year-round with proper care.
  - **Care:** Prefers full sun and well-drained soil, regular watering is essential.

### 6. **Neem (Azadirachta indica)**
  - **Effectiveness:** Medium
  - **Why:** Neem is a natural insect repellent due to compounds like azadirachtin. While not as potent as citronella, it can still help keep mosquitoes at bay.
  - **Growth:** Thrives in tropical climates and is often used in organic pest control.
  - **Care:** Needs well-drained soil and a sunny location.

### 7. **Peppermint (Mentha × piperita)**
  - **Effectiveness:** Medium
  - **Why:** Peppermint’s strong scent is disliked by mosquitoes and other pests.
  - **Growth:** Can be easily grown in pots or garden beds in Southeast Asia. It spreads quickly, so be mindful of controlling its growth.
  - **Care:** Requires partial shade, frequent watering, and moist soil.

### 8. **Rosemary (Rosmarinus officinalis)**
  - **Effectiveness:** Medium
  - **Why:** The strong aroma of rosemary helps repel mosquitoes, though it is not as effective as citronella or lemongrass.
  - **Growth:** Prefers sunny locations and well-drained soil. Can thrive in Southeast Asia’s climate with some care.
  - **Care:** Needs full sun and moderate watering.

### 9. **Garlic (Allium sativum)**
  - **Effectiveness:** Medium-Low
  - **Why:** Garlic has sulfur compounds that can deter mosquitoes when planted around the garden. While not a top-tier repellent, it helps in the fight against pests.
  - **Growth:** Can be planted easily in Southeast Asia and has minimal maintenance requirements.
  - **Care:** Needs full sun and well-drained soil.

### 10. **Catnip (Nepeta cataria)**
  - **Effectiveness:** Medium-Low
  - **Why:** While catnip is more effective against other pests, it has a mild mosquito-repelling property due to a compound called nepetalactone.
  - **Growth:** It grows easily in Southeast Asia’s climate and thrives with minimal care.
  - **Care:** Needs full sun and well-drained soil.

### Tips for Planting in Southeast Asia:
- Most of these plants thrive in Southeast Asia's tropical and subtropical climate, but ensure they are planted in a spot with adequate sunlight and drainage.
- Regular watering and well-maintained soil are essential for their growth.
- You can plant them in pots or directly in the garden depending on space and convenience.

Using these plants around your home or garden can help reduce mosquito presence and add a pleasant natural fragrance to your surroundings.